Optical lens set

ABSTRACT

An optical-lens-set includes a first lens element of positive refractive power, a second lens element of an image surface with a concave portion near the optical-axis, no air gap between a third lens element and a fourth lens element, at least one of an object surface and an image surface of a fifth lens element being aspherical, both an object surface and an image surface of a sixth lens element being aspherical so that the total thickness ALT of all six lens element, the distance TL from an object surface of the first lens element to the image surface of the sixth lens element and total five air gaps AAG satisfy ALT/AAG≤4.5 or TL/AAG≤5.5.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Chinese patent application No.201610948407.6, filed on Nov. 2, 2016. The contents of which are herebyincorporated by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to an optical imaging lens set.Specifically speaking, the present invention is directed to an opticalimaging lens set for use in portable electronic devices such as mobilephones, cameras, tablet personal computers, or personal digitalassistants (PDA) for taking pictures and for recording videos.

2. Description of the Prior Art

The specifications of portable electronic devices change all the timeand the key element—optical imaging lens set develops variously so agood imaging quality is needed as well as a larger aperture stop andwider view angles. As far as the increase of view angles and aperturestop are concerned, flare usually happens due to the total reflection ofincoming light passing through the first three lens elements. Inaddition, in order to correct the spherical aberration and the chromaticaberration which are caused by the first two lens elements, there arevarious injection molding problems, such as smaller thickness of thethird lens element and the fourth lens element or heavily crookedperiphery curves of the third lens element and the fourth lens element.

SUMMARY OF THE INVENTION

In light of the above, the present invention proposes an optical imaginglens set of six lens elements which is shorter in total length,technically possible, has reduced air gaps, has low flare and has goodoptical performance. The optical imaging lens set of six lens elementsof the present invention from an object side toward an image side inorder along an optical axis has a first lens element, a second lenselement, a third lens element, a fourth lens element, a fifth lenselement and a sixth lens element. Each lens element respectively has anobject-side surface which faces toward an object side as well as animage-side surface which faces toward an image side.

In a first aspect, the first lens element has positive refractive power.The second lens element has an image-side surface with a concave portionin a vicinity of the optical-axis. There is no air gap between the thirdlens element and the fourth lens element. At least one of theobject-side surface and the image-side surface of the fifth lens elementis aspherical. Both the object-side surface and the image-side surfaceof the sixth lens element are aspherical.

The optical imaging lens set exclusively has the first lens element, thesecond lens element, the third lens element, the fourth lens element,the fifth lens element and the sixth lens element with refractive power.TL is a distance between the object-side surface of the first lenselement and the image-side surface of the sixth lens element along theoptical axis and AAG is a sum of all air gaps disposed between adjacentlens elements from the first lens element to the sixth lens elementalong the optical axis to satisfy TL/AAG≤5.5.

The present invention in a second aspect proposes another opticalimaging lens set of six lens elements which is shorter in total length,technically possible, has reduced air gaps, has low flare and has goodoptical performance. The optical imaging lens set of six lens elementsfrom an object side toward an image side in order along an optical axishas a first lens element, a second lens element, a third lens element, afourth lens element, a fifth lens element and a sixth lens element. Eachlens element respectively has an object-side surface facing toward anobject side as well as an image-side surface facing toward an imageside.

The first lens element has positive refractive power. The second lenselement has an image-side surface with a concave portion in a vicinityof the optical-axis. There is no air gap between the third lens elementand the fourth lens element. At least one of the object-side surface andthe image-side surface of the fifth lens element is aspherical. Both theobject-side surface and the image-side surface of the sixth lens elementare aspherical. The optical imaging lens set exclusively has the firstlens element, the second lens element, the third lens element, thefourth lens element, the fifth lens element and the sixth lens elementwith refractive power. ALT is a total thickness of all six lens elementsalong the optical axis and AAG is a sum of all four air gaps which aredisposed between adjacent lens elements from the first lens element tothe sixth lens element along the optical axis to satisfy ALT/AAG≤4.5.

In the optical imaging lens set of six lens elements of the presentinvention, υ3 is an Abbe number of the third lens element and υ4 is anAbbe number of the fourth lens element to satisfy 16≤υ3−υ4≤50.

In the optical imaging lens set of six lens elements of the presentinvention, the first lens element has a first lens element thickness T₁along the optical axis and an air gap G₂₃ between the second lenselement and the third lens element along the optical axis to satisfyT₁/G₂₃≤2.4.

In the optical imaging lens set of six lens elements of the presentinvention, an air gap G₁₂ between the first lens element and the secondlens element along the optical axis and an air gap G₄₅ between thefourth lens element and the fifth lens element along the optical axis tosatisfy (T₁+G₁₂)/G₄₅≤2.15.

In the optical imaging lens set of six lens elements of the presentinvention, the second lens element has a second lens element thicknessT₂ along the optical axis and the third lens element has a third lenselement thickness T₃ along the optical axis to satisfy(T₁+G₁₂+T₂)/T₃≤2.75.

In the optical imaging lens set of six lens elements of the presentinvention, the fourth lens element has a fourth lens element thicknessT₄ along the optical axis, an air gap G₃₄ between the third lens elementand the fourth lens element along the optical axis and an air gap G₅₅between the fifth lens element and the sixth lens element along theoptical axis to satisfy (T₂+T₄)/(G₁₂+G₃₄+G₅₆)≤3.8.

The optical imaging lens set of six lens elements of the presentinvention satisfies AAG/T₁≤3.45.

The optical imaging lens set of six lens elements of the presentinvention satisfies AAG/T₄≤4.8.

In the optical imaging lens set of six lens elements of the presentinvention, EFL is an effective focal length of the optical imaging lensset and the sixth lens element has a sixth lens element thickness T₅along the optical axis to satisfy EFL/(T₁+T₆)≤4.15.

In the optical imaging lens set of six lens elements of the presentinvention, EPD is an entrance pupil diameter of an aperture stop tosatisfy ALT/EPD≤1.75.

In the optical imaging lens set of six lens elements of the presentinvention, the first lens element has a first lens element thickness T₁along the optical axis and an air gap G₄₅ between the fourth lenselement and the fifth lens element along the optical axis to satisfy tosatisfy T₁/G₄₅≤1.95.

In the optical imaging lens set of six lens elements of the presentinvention, an air gap G₁₂ between the first lens element and the secondlens element along the optical axis and an air gap G₂₃ between thesecond lens element and the third lens element along the optical axis tosatisfy (T₁+G₁₂)/G₂₃≤2.65.

In the optical imaging lens set of six lens elements of the presentinvention, the second lens element has a second lens element thicknessT₂ along the optical axis and the fifth lens element has a fifth lenselement thickness T₅ along the optical axis to satisfy(T₁+G₁₂+T₂)/T₅≤1.85.

In the optical imaging lens set of six lens elements of the presentinvention, an air gap G₃₄ between the third lens element and the fourthlens element along the optical axis and an air gap G₅₅ between the fifthlens element and the sixth lens element along the optical axis tosatisfy T₅/(G₁₂+G₃₄+G₅₆)≤4.

The optical imaging lens set of six lens elements of the presentinvention satisfies (T₂+G₂₃)/(G₁₂+G₃₄+G₅₆)≤3.3.

The optical imaging lens set of six lens elements of the presentinvention satisfies AAG/T₂≤5.7.

In the optical imaging lens set of six lens elements of the presentinvention, the sixth lens element has a sixth lens element thickness T₆along the optical axis to satisfy AAG/T₆≤3.6.

In the optical imaging lens set of six lens elements of the presentinvention, EFL is an effective focal length of the optical imaging lensset and the third lens element has a third lens element thickness T₃along the optical axis to satisfy EFL/(T₃+T₅)≤5.15.

In the optical imaging lens set of six lens elements of the presentinvention, EPD is an entrance pupil diameter of an aperture stop tosatisfy TL/EPD≤4.5.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 illustrates the methods for determining the surface shapes andfor determining one region is a region in a vicinity of the optical axisor the region in a vicinity of its circular periphery of one lenselement.

FIG. 6 illustrates a first example of the optical imaging lens set ofthe present invention.

FIG. 7A illustrates the longitudinal spherical aberration on the imageplane of the first example.

FIG. 7B illustrates the astigmatic aberration on the sagittal directionof the first example.

FIG. 7C illustrates the astigmatic aberration on the tangentialdirection of the first example.

FIG. 7D illustrates the distortion aberration of the first example.

FIG. 8 illustrates a second example of the optical imaging lens set offive lens elements of the present invention.

FIG. 9A illustrates the longitudinal spherical aberration on the imageplane of the second example.

FIG. 9B illustrates the astigmatic aberration on the sagittal directionof the second example.

FIG. 9C illustrates the astigmatic aberration on the tangentialdirection of the second example.

FIG. 9D illustrates the distortion aberration of the second example.

FIG. 10 illustrates a third example of the optical imaging lens set offive lens elements of the present invention.

FIG. 11A illustrates the longitudinal spherical aberration on the imageplane of the third example.

FIG. 11B illustrates the astigmatic aberration on the sagittal directionof the third example.

FIG. 11C illustrates the astigmatic aberration on the tangentialdirection of the third example.

FIG. 11D illustrates the distortion aberration of the third example.

FIG. 12 illustrates a fourth example of the optical imaging lens set offive lens elements of the present invention.

FIG. 13A illustrates the longitudinal spherical aberration on the imageplane of the fourth example.

FIG. 13B illustrates the astigmatic aberration on the sagittal directionof the fourth example.

FIG. 13C illustrates the astigmatic aberration on the tangentialdirection of the fourth example.

FIG. 13D illustrates the distortion aberration of the fourth example.

FIG. 14 illustrates a fifth example of the optical imaging lens set offive lens elements of the present invention.

FIG. 15A illustrates the longitudinal spherical aberration on the imageplane of the fifth example.

FIG. 15B illustrates the astigmatic aberration on the sagittal directionof the fifth example.

FIG. 15C illustrates the astigmatic aberration on the tangentialdirection of the fifth example.

FIG. 15D illustrates the distortion aberration of the fifth example.

FIG. 16 illustrates a sixth example of the optical imaging lens set offive lens elements of the present invention.

FIG. 17A illustrates the longitudinal spherical aberration on the imageplane of the sixth example.

FIG. 17B illustrates the astigmatic aberration on the sagittal directionof the sixth example.

FIG. 17C illustrates the astigmatic aberration on the tangentialdirection of the sixth example.

FIG. 17D illustrates the distortion aberration of the sixth example.

FIG. 18 illustrates a seventh example of the optical imaging lens set offive lens elements of the present invention.

FIG. 19A illustrates the longitudinal spherical aberration on the imageplane of the seventh example.

FIG. 19B illustrates the astigmatic aberration on the sagittal directionof the seventh example.

FIG. 19C illustrates the astigmatic aberration on the tangentialdirection of the seventh example.

FIG. 19D illustrates the distortion aberration of the seventh example.

FIG. 20 illustrates an eighth example of the optical imaging lens set offive lens elements of the present invention.

FIG. 21A illustrates the longitudinal spherical aberration on the imageplane of the eighth example.

FIG. 21B illustrates the astigmatic aberration on the sagittal directionof the eighth example.

FIG. 21C illustrates the astigmatic aberration on the tangentialdirection of the eighth example.

FIG. 21D illustrates the distortion aberration of the eighth example.

FIG. 22 illustrates a ninth example of the optical imaging lens set offive lens elements of the present invention.

FIG. 23A illustrates the longitudinal spherical aberration on the imageplane of the ninth example.

FIG. 23B illustrates the astigmatic aberration on the sagittal directionof the ninth example.

FIG. 23C illustrates the astigmatic aberration on the tangentialdirection of the ninth example.

FIG. 23D illustrates the distortion aberration of the ninth example.

FIG. 24 shows the optical data of the first example of the opticalimaging lens set.

FIG. 25 shows the aspheric surface data of the first example.

FIG. 26 shows the optical data of the second example of the opticalimaging lens set.

FIG. 27 shows the aspheric surface data of the second example.

FIG. 28 shows the optical data of the third example of the opticalimaging lens set.

FIG. 29 shows the aspheric surface data of the third example.

FIG. 30 shows the optical data of the fourth example of the opticalimaging lens set.

FIG. 31 shows the aspheric surface data of the fourth example.

FIG. 32 shows the optical data of the fifth example of the opticalimaging lens set.

FIG. 33 shows the aspheric surface data of the fifth example.

FIG. 34 shows the optical data of the sixth example of the opticalimaging lens set.

FIG. 35 shows the aspheric surface data of the sixth example.

FIG. 36 shows the optical data of the seventh example of the opticalimaging lens set.

FIG. 37 shows the aspheric surface data of the seventh example.

FIG. 38 shows the optical data of the eighth example of the opticalimaging lens set.

FIG. 39 shows the aspheric surface data of the eighth example.

FIG. 40 shows the optical data of the ninth example of the opticalimaging lens set.

FIG. 41 shows the aspheric surface data of the ninth example.

FIG. 42 shows some important ratios in the examples.

DETAILED DESCRIPTION

Before the detailed description of the present invention, the firstthing to be noticed is that in the present invention, similar (notnecessarily identical) elements are labeled as the same numeralreferences. In the entire present specification, “a certain lens elementhas negative/positive refractive power” refers to the part in a vicinityof the optical axis of the lens element has negative/positive refractivepower calculated by Gaussian optical theory. An object-side/image-sidesurface refers to the region which allows imaging light passing through,in the drawing, imaging light includes Lc (chief ray) and Lm (marginalray). As shown in FIG. 1, the optical axis is “I” and the lens elementis symmetrical with respect to the optical axis I. The region A thatnear the optical axis and for light to pass through is the region in avicinity of the optical axis, and the region C that the marginal raypassing through is the region in a vicinity of a certain lens element'scircular periphery. In addition, the lens element may include anextension part E for the lens element to be installed in an opticalimaging lens set (that is the region outside the region C perpendicularto the optical axis). Ideally speaking, no light would pass through theextension part, and the actual structure and shape of the extension partis not limited to this and may have other variations. For the reason ofsimplicity, the extension part is not illustrated in the followingexamples. More, precisely, the method for determining the surface shapesor the region in a vicinity of the optical axis, the region in avicinity of its circular periphery and other regions is described in thefollowing paragraphs:

1. FIG. 1 is a radial cross-sectional view of a lens element. Beforedetermining boundaries of those aforesaid portions, two referentialpoints should be defined first, middle point and conversion point. Themiddle point of a surface of a lens element is a point of intersectionof that surface and the optical axis. The conversion point is a point ona surface of a lens element, where the tangent line of that point isperpendicular to the optical axis. Additionally, if multiple conversionpoints appear on one single surface, then these conversion points aresequentially named along the radial direction of the surface withnumbers starting from the first conversion point. For instance, thefirst conversion point (closest one to the optical axis), the secondconversion point, and the N^(th) conversion point (farthest one to theoptical axis within the scope of the clear aperture of the surface). Theportion of a surface of the lens element between the middle point andthe first conversion point is defined as the portion in a vicinity ofthe optical axis. The portion located radially outside of the N^(th)conversion point (but still within the scope of the clear aperture) isdefined as the portion in a vicinity of a periphery of the lens element.In some embodiments, there are other portions existing between theportion in a vicinity of the optical axis and the portion in a vicinityof a periphery of the lens element; the numbers of portions depend onthe numbers of the conversion point(s). In addition, the radius of theclear aperture (or a so-called effective radius) of a surface is definedas the radial distance from the optical axis I to a point ofintersection of the marginal ray Lm and the surface of the lens element.2. Referring to FIG. 2, determining the shape of a portion is convex orconcave depends on whether a collimated ray passing through that portionconverges or diverges. That is, while applying a collimated ray to aportion to be determined in terms of shape, the collimated ray passingthrough that portion will be bended and the ray itself or its extensionline will eventually meet the optical axis. The shape of that portioncan be determined by whether the ray or its extension line meets(intersects) the optical axis (focal point) at the object-side orimage-side. For instance, if the ray itself intersects the optical axisat the image side of the lens element after passing through a portion,i.e. the focal point of this ray is at the image side (see point R inFIG. 2), the portion will be determined as having a convex shape. On thecontrary, if the ray diverges after passing through a portion, theextension line of the ray intersects the optical axis at the object sideof the lens element, i.e. the focal point of the ray is at the objectside (see point M in FIG. 2), that portion will be determined as havinga concave shape. Therefore, referring to FIG. 2, the portion between themiddle point and the first conversion point has a convex shape, theportion located radially outside of the first conversion point has aconcave shape, and the first conversion point is the point where theportion having a convex shape changes to the portion having a concaveshape, namely the border of two adjacent portions. Alternatively, thereis another common way for a person with ordinary skill in the art totell whether a portion in a vicinity of the optical axis has a convex orconcave shape by referring to the sign of an “R” value, which is the(paraxial) radius of curvature of a lens surface. The R value iscommonly used in conventional optical design software such as Zemax andCodeV. The R value usually appears in the lens data sheet in thesoftware. For an object-side surface, positive R means that theobject-side surface is convex, and negative R means that the object-sidesurface is concave. Conversely, for an image-side surface, positive Rmeans that the image-side surface is concave, and negative R means thatthe image-side surface is convex. The result found by using this methodshould be consistent as by using the other way mentioned above, whichdetermines surface shapes by referring to whether the focal point of acollimated ray is at the object side or the image side.3. For none conversion point cases, the portion in a vicinity of theoptical axis is defined as the portion between 0˜50% of the effectiveradius (radius of the clear aperture) of the surface, whereas theportion in a vicinity of a periphery of the lens element is defined asthe portion between 50˜100% of effective radius (radius of the clearaperture) of the surface.

Referring to the first example depicted in FIG. 3, only one conversionpoint, namely a first conversion point, appears within the clearaperture of the image-side surface of the lens element. Portion I is aportion in a vicinity of the optical axis, and portion II is a portionin a vicinity of a periphery of the lens element. The portion in avicinity of the optical axis is determined as having a concave surfacedue to the R value at the image-side surface of the lens element ispositive. The shape of the portion in a vicinity of a periphery of thelens element is different from that of the radially inner adjacentportion, i.e. the shape of the portion in a vicinity of a periphery ofthe lens element is different from the shape of the portion in avicinity of the optical axis; the portion in a vicinity of a peripheryof the lens element has a convex shape.

Referring to the second example depicted in FIG. 4, a first conversionpoint and a second conversion point exist on the object-side surface(within the clear aperture) of a lens element. In which portion I is theportion in a vicinity of the optical axis, and portion III is theportion in a vicinity of a periphery of the lens element. The portion ina vicinity of the optical axis has a convex shape because the R value atthe object-side surface of the lens element is positive. The portion ina vicinity of a periphery of the lens element (portion III) has a convexshape. What is more, there is another portion having a concave shapeexisting between the first and second conversion point (portion II).

Referring to a third example depicted in FIG. 5, no conversion pointexists on the object-side surface of the lens element. In this case, theportion between 0˜50% of the effective radius (radius of the clearaperture) is determined as the portion in a vicinity of the opticalaxis, and the portion between 50˜100% of the effective radius isdetermined as the portion in a vicinity of a periphery of the lenselement. The portion in a vicinity of the optical axis of theobject-side surface of the lens element is determined as having a convexshape due to its positive R value, and the portion in a vicinity of aperiphery of the lens element is determined as having a convex shape aswell.

As shown in FIG. 6, the optical imaging lens set 1 of six lens elementsof the present invention, sequentially located from an object side 2(where an object is located) to an image side 3 along an optical axis 4,has an aperture stop (ape. stop) 80, a first lens element 10, a secondlens element 20, a third lens element 30, a fourth lens element 40, afifth lens element 50, a sixth lens element 60, a filter 70 and an imageplane 71. Generally speaking, the first lens element 10, the second lenselement 20, the third lens element 30, the fourth lens element 40, thefifth lens element 50 and the sixth lens element 60 may be made of atransparent plastic material but the present invention is not limited tothis, and each has an appropriate refractive power. There areexclusively six lens elements, which means the first lens element 10,the second lens element 20, the third lens element 30, the fourth lenselement 40, the fifth lens element 50 and the sixth lens element 60,with refractive power in the optical imaging lens set 1 of the presentinvention. The optical axis 4 is the optical axis of the entire opticalimaging lens set 1, and the optical axis of each of the lens elementscoincides with the optical axis of the optical imaging lens set 1.

Furthermore, the optical imaging lens set 1 includes an aperture stop(ape. stop) 80 disposed in an appropriate position. In FIG. 6, theaperture stop 80 is disposed between the object side 2 and the firstlens element 10. When light emitted or reflected by an object (notshown) which is located at the object side 2 enters the optical imaginglens set 1 of the present invention, it forms a clear and sharp image onthe image plane 71 at the image side 3 after passing through theaperture stop 80, the first lens element 10, the second lens element 20,the third lens element 30, the fourth lens element 40, the fifth lenselement 50, the sixth lens element 60 and the filter 70. In oneembodiments of the present invention, the optional filter 70 may be afilter of various suitable functions, for example, the filter 70 may bean infrared cut filter (IR cut filter), placed between the image-sidesurface 62 of the sixth lens element 60 and the image plane 71.

Each lens element in the optical imaging lens set 1 of the presentinvention has an object-side surface facing toward the object side 2 aswell as an image-side surface facing toward the image side 3. Forexample, the first lens element 10 has an object-side surface 11 and animage-side surface 12; the second lens element 20 has an object-sidesurface 21 and an image-side surface 22; the third lens element 30 hasan object-side surface 31 and an image-side surface 32; the fourth lenselement 40 has an object-side surface 41 and an image-side surface 42;the fifth lens element 50 has an object-side surface 51 and animage-side surface 52; the sixth lens element 60 has an object-sidesurface 61 and an image-side surface 62. In addition, each object-sidesurface and image-side surface in the optical imaging lens set 1 of thepresent invention has a part (or portion) in a vicinity of its circularperiphery (circular periphery part) away from the optical axis 4 as wellas a part in a vicinity of the optical axis (optical axis part) close tothe optical axis 4.

Each lens element in the optical imaging lens set 1 of the presentinvention further has a central thickness T on the optical axis 4. Forexample, the first lens element 10 has a first lens element thicknessT₁, the second lens element 20 has a second lens element thickness T₂,the third lens element 30 has a third lens element thickness T₃, thefourth lens element 40 has a fourth lens element thickness T₄, the fifthlens element 50 has a fifth lens element thickness T₅, the sixth lenselement 60 has a sixth lens element thickness T₅. Therefore, the totalthickness of all the lens elements in the optical imaging lens set 1along the optical axis 4 is ALT=T₁+T₂+T₃+T₄+T₅+T₆.

In addition, between two adjacent lens elements in the optical imaginglens set 1 of the present invention there may be an air gap along theoptical axis 4. For example, there is an air gap G₁₂ disposed betweenthe first lens element 10 and the second lens element 20, an air gap G₂₃disposed between the second lens element 20 and the third lens element30, an air gap G₄₅ disposed between the fourth lens element 40 and thefifth lens element 50 as well as there is an air gap G₅₆ disposedbetween the fifth lens element 50 and the sixth lens element 60 butthere is no air gap G₃₄ disposed between the third lens element 30 andthe fourth lens element 40 so G₃₄ is 0. Therefore, the sum of total fourair gaps between adjacent lens elements from the first lens element 10to the sixth lens element 60 along the optical axis 4 isAAG=G₁₂+G₂₃+G₄₅+G₅₆.

In addition, the distance from the object-side surface 11 of the firstlens element 10 to the image-side surface 62 of the sixth lens element60 along the optical axis 4 is TL. The distance between the object-sidesurface 11 of the first lens element 10 to the image plane 71, namelythe total length of the optical imaging lens set along the optical axis4 is TTL; the effective focal length of the optical imaging lens set isEFL; the distance between the image-side surface 62 of the sixth lenselement 60 and the image plane 71 along the optical axis 4 is BFL. EPDis an entrance pupil diameter of the aperture stop 80.

Furthermore, the focal length of the first lens element 10 is f1; thefocal length of the second lens element 20 is f2; the focal length ofthe third lens element 30 is f3; the focal length of the fourth lenselement 40 is f4; the focal length of the fifth lens element 50 is f5;the focal length of the sixth lens element 60 is f6; the refractiveindex of the first lens element 10 is n1; the refractive index of thesecond lens element 20 is n2; the refractive index of the third lenselement 30 is n3; the refractive index of the fourth lens element 40 isn4; the refractive index of the fifth lens element 50 is n5; therefractive index of the sixth lens element 60 is n6; the Abbe number ofthe first lens element 10 is υ1; the Abbe number of the second lenselement 20 is υ2; the Abbe number of the third lens element 30 is υ3;and the Abbe number of the fourth lens element 40 is υ4; the Abbe numberof the fifth lens element 50 is υ5; and the Abbe number of the sixthlens element 60 is υ6.

First Example

Please refer to FIG. 6 which illustrates the first example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 7A for the longitudinal spherical aberration on the image plane 71of the first example; please refer to FIG. 7B for the astigmatic fieldaberration on the sagittal direction; please refer to FIG. 7C for theastigmatic field aberration on the tangential direction, and pleaserefer to FIG. 7D for the distortion aberration. The Y axis of thespherical aberration in each example is “field of view” for 1.0. The Yaxis of the astigmatic field and the distortion in each example standsfor “image height”, which is 3.528 mm.

The optical imaging lens set 1 of the first example has six lenselements 10 to 60 with refractive power. The optical imaging lens set 1also has a filter 70, an aperture stop 80, and an image plane 71. Theaperture stop 80 is provided between the object side 2 and the firstlens element 10. The filter 70 may be used for preventing specificwavelength light (such as the infrared light) reaching the image planeto adversely affect the imaging quality.

The first lens element 10 has positive refractive power. The object-sidesurface 11 facing toward the object side 2 has a convex part 13 in thevicinity of the optical axis and a convex part 14 in a vicinity of itscircular periphery. The image-side surface 12 facing toward the imageside 3 has a concave part 16 in the vicinity of the optical axis and aconcave part 17 in a vicinity of its circular periphery. Besides, boththe object-side surface 11 and the image-side 12 are asphericalsurfaces.

The second lens element 20 is of a plastic material and has negativerefractive power. The object-side surface 21 facing toward the objectside 2 has a convex part 23 in the vicinity of the optical axis and aconvex part 24 in a vicinity of its circular periphery. The image-sidesurface 22 facing toward the image side 3 has a concave part 26 in thevicinity of the optical axis and a concave part 27 in a vicinity of itscircular periphery. Besides, both the object-side surface 21 and theimage-side 22 of the second lens element 20 are aspherical surfaces.

The third lens element 30 has negative refractive power. The object-sidesurface 31 facing toward the object side 2 has a concave part 33 in thevicinity of the optical axis and a concave part 34 in a vicinity of itscircular periphery. The image-side surface 32 facing toward the imageside 3 has a convex part 36 in the vicinity of the optical axis and aconvex part 37 in a vicinity of its circular periphery. The object-sidesurface 31 of the third lens element 30 is an aspherical surface.

The fourth lens element 40 has positive refractive power. Theobject-side surface 41 facing toward the object side 2 has a concavepart 43 in the vicinity of the optical axis and a concave part 44 in avicinity of its circular periphery. The image-side surface 42 facingtoward the image side 3 has a convex part 46 in the vicinity of theoptical axis and a convex part 47 in a vicinity of its circularperiphery. The image-side 42 of the fourth lens element 40 is anaspherical surface. The third lens element 30 and the fourth lenselement 40 may be attached together with glue or a film so there is noair gap between the image-side surface 32 of the third lens element 30and the object-side surface 41 of the fourth lens element 40.

The fifth lens element 50 has positive refractive power. The object-sidesurface 51 facing toward the object side 2 has a concave part 53 in thevicinity of the optical axis and a concave part 54 in a vicinity of itscircular periphery. The image-side surface 52 facing toward the imageside 3 has a convex part 56 in the vicinity of the optical axis and aconvex part 57 in a vicinity of its circular periphery. Besides, atleast one of the object-side surface 51 and the image-side 52 of thefifth lens element 50 is an aspherical surface.

The sixth lens element 60 has negative refractive power. The object-sidesurface 61 facing toward the object side 2 has a convex part 63 in thevicinity of the optical axis and a concave part 64 in a vicinity of itscircular periphery. The image-side surface 62 facing toward the imageside 3 has a concave part 66 in the vicinity of the optical axis and aconvex part 67 in a vicinity of its circular periphery. Both theobject-side surface 61 and the image-side 62 of the sixth lens element60 are aspherical surfaces. The filter 70 is disposed between theimage-side 62 of the sixth lens element 60 and the image plane 71.

In the first lens element 10, the second lens element 20, the third lenselement 30, the fourth lens element 40, the fifth lens element 50 andthe sixth lens element 60 of the optical imaging lens element 1 of thepresent invention, there are 12 surfaces, such as the object-sidesurfaces 11/21/31/41/51/61 and the image-side surfaces12/22/32/42/52/62. If a surface is aspherical, these asphericcoefficients are defined according to the following formula:

${Z(Y)} = {{\frac{Y^{2}}{R}/\left( {1 + \sqrt{1 - {\left( {1 + K} \right)\frac{Y^{2}}{R^{2}}}}} \right)} + {\sum\limits_{i = 1}^{n}{a_{i} \times Y^{i}}}}$In which:R represents the curvature radius of the lens element surface;Z represents the depth of an aspherical surface (the perpendiculardistance between the point of the aspherical surface at a distance Yfrom the optical axis and the tangent plane of the vertex on the opticalaxis of the aspherical surface);Y represents a vertical distance from a point on the aspherical surfaceto the optical axis;K is a conic constant;a_(i) is the aspheric coefficient of the i^(th) order.

The optical data of the first example of the optical imaging lens set 1are shown in FIG. 24 while the aspheric surface data are shown in FIG.25. In the present examples of the optical imaging lens set, thef-number of the entire optical lens element system is Fno, EFL is theeffective focal length, HFOV stands for the half field of view which ishalf of the field of view of the entire optical lens element system, andthe unit for the curvature radius, the thickness and the focal length isin millimeters (mm). TTL is 5.3323 mm. Fno is 1.6740. The image heightis 3.528 mm. HFOV is 38.5720 degrees.

Second Example

Please refer to FIG. 8 which illustrates the second example of theoptical imaging lens set 1 of the present invention. It is noted thatfrom the second example to the following examples, in order to simplifythe figures, only the components different from what the first examplehas, and the basic lens elements will be labeled in figures. Othercomponents that are the same as what the first example has, such as theobject-side surface, the image-side surface, the part in a vicinity ofthe optical axis and the part in a vicinity of its circular peripherywill be omitted in the following examples. Please refer to FIG. 9A forthe longitudinal spherical aberration on the image plane 71 of thesecond example, please refer to FIG. 9B for the astigmatic aberration onthe sagittal direction, please refer to FIG. 9C for the astigmaticaberration on the tangential direction, and please refer to FIG. 9D forthe distortion aberration. The components in the second example aresimilar to those in the first example, but the optical data such as thecurvature radius, the refractive power, the lens thickness, the lensfocal length, the aspheric surface or the back focal length in thisexample are different from the optical data in the first example, and inthis example, the third lens element 30 has positive refractive power,the object-side surface 31 of the third lens element 30 facing towardthe object side 2 has a convex part 33′ in the vicinity of the opticalaxis and the object-side surface 61 of the sixth lens element 60 facingtoward the object side 2 has a concave part 63′ in the vicinity of theoptical axis.

The optical data of the second example of the optical imaging lens setare shown in FIG. 26 while the aspheric surface data are shown in FIG.27. TTL is 5.0778 mm. Fno is 1.6971. The image height is 3.528 mm. HFOVis 42.2740 degrees. In particular, 1) the TTL of the second example isshorter than that of the first example of the present invention, 2) theHFOV of the second example is better than that of the first example ofthe present invention.

Third Example

Please refer to FIG. 10 which illustrates the third example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 11A for the longitudinal spherical aberration on the image plane 71of the third example; please refer to FIG. 11B for the astigmaticaberration on the sagittal direction; please refer to FIG. 11C for theastigmatic aberration on the tangential direction, and please refer toFIG. 11D for the distortion aberration. The components in the thirdexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the object-side surface 31 of the third lenselement 30 facing toward the object side 2 has a convex part 33′ in thevicinity of the optical axis and the object-side surface 61 of the sixthlens element 60 facing toward the object side 2 has a convex 64′ in avicinity of its circular periphery.

The optical data of the third example of the optical imaging lens setare shown in FIG. 28 while the aspheric surface data are shown in FIG.29. TTL is 5.5551 mm. Fno is 1.8078. The image height is 3.528 mm. HFOVis 43.1208 degrees. In particular, the HFOV of the third example isbetter than that of the first example of the present invention.

Fourth Example

Please refer to FIG. 12 which illustrates the fourth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 13A for the longitudinal spherical aberration on the image plane 71of the fourth example; please refer to FIG. 13B for the astigmaticaberration on the sagittal direction; please refer to FIG. 13C for theastigmatic aberration on the tangential direction, and please refer toFIG. 13D for the distortion aberration. The components in the fourthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the object-side surface 31 of the third lenselement 30 facing toward the object side 2 has a convex part 33′ in thevicinity of the optical axis and a convex part 34′ in a vicinity of itscircular periphery, and the object-side surface 51 of the fifth lenselement 50 facing toward the object side 2 has a convex part 53′ in thevicinity of the optical axis.

The optical data of the fourth example of the optical imaging lens setare shown in FIG. 30 while the aspheric surface data are shown in FIG.31. TTL is 5.4516 mm. Fno is 1.7041. The image height is 3.528 mm. HFOVis 41.6654 degrees. In particular, the HFOV of the fourth example islarger than that of the first example of the present invention.

Fifth Example

Please refer to FIG. 14 which illustrates the fifth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 15A for the longitudinal spherical aberration on the image plane 71of the fifth example; please refer to FIG. 15B for the astigmaticaberration on the sagittal direction; please refer to FIG. 15C for theastigmatic aberration on the tangential direction, and please refer toFIG. 15D for the distortion aberration. The components in the fifthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the object-side surface 31 of the third lenselement 30 facing toward the object side 2 has a convex part 33′ in thevicinity of the optical axis.

The optical data of the fifth example of the optical imaging lens setare shown in FIG. 32 while the aspheric surface data are shown in FIG.33. TTL is 4.9785 mm. Fno is 1.7114. The image height is 3.528 mm. HFOVis 41.9604 degrees. In particular, 1) the TTL of the fifth example isshorter than that of the first example of the present invention, 2) theHFOV of the fifth example is better than that of the first example ofthe present invention, 3) the imaging quality of the fifth example isbetter than that of the first example of the present invention.

Sixth Example

Please refer to FIG. 16 which illustrates the sixth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 17A for the longitudinal spherical aberration on the image plane 71of the sixth example; please refer to FIG. 17B for the astigmaticaberration on the sagittal direction; please refer to FIG. 17C for theastigmatic aberration on the tangential direction, and please refer toFIG. 17D for the distortion aberration. The components in the sixthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the object-side surface 31 of the third lenselement 30 facing toward the object side 2 has a convex part 33′ in thevicinity of the optical axis, the object-side surface 51 of the fifthlens element 50 facing toward the object side 2 has a convex part 53′ inthe vicinity of the optical axis and the object-side surface 61 of thesixth lens element 60 facing toward the object side 2 has a concave part63′ in the vicinity of the optical axis.

The optical data of the sixth example of the optical imaging lens setare shown in FIG. 34 while the aspheric surface data are shown in FIG.35. TTL is 5.5487 mm. Fno is 1.7123. The image height is 3.528 mm. HFOVis 42.9492 degrees. In particular, the HFOV of the sixth example isbetter than that of the first example of the present invention.

Seventh Example

Please refer to FIG. 18 which illustrates the seventh example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 19A for the longitudinal spherical aberration on the image plane 71of the seventh example; please refer to FIG. 19B for the astigmaticaberration on the sagittal direction; please refer to FIG. 19C for theastigmatic aberration on the tangential direction, and please refer toFIG. 19D for the distortion aberration. The components in the seventhexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the object-side surface 31 of the third lenselement 30 facing toward the object side 2 has a convex part 33′ in thevicinity of the optical axis and the object-side surface 51 of the fifthlens element 50 facing toward the object side 2 has a convex part 53′ inthe vicinity of the optical axis.

The optical data of the seventh example of the optical imaging lens setare shown in FIG. 36 while the aspheric surface data are shown in FIG.37. TTL is 5.3528 mm. Fno is 1.7167. The image height is 3.528 mm. HFOVis 45.7400 degrees. In particular, the HFOV of the seventh example isbetter than that of the first example of the present invention.

Eighth Example

Please refer to FIG. 20 which illustrates the eighth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 21A for the longitudinal spherical aberration on the image plane 71of the eighth example; please refer to FIG. 21B for the astigmaticaberration on the sagittal direction; please refer to FIG. 21C for theastigmatic aberration on the tangential direction, and please refer toFIG. 21D for the distortion aberration. The components in the eighthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the third lens element 30 has positive refractivepower, the fourth lens element 40 has negative refractive power, theobject-side surface 31 of the third lens element 30 facing toward theobject side 2 has a convex part 33′ in the vicinity of the optical axisand the image-side surface 42 of the fourth lens element 40 facingtoward the image side 3 has a concave part 47′ in a vicinity of itscircular periphery.

The optical data of the eighth example of the optical imaging lens setare shown in FIG. 38 while the aspheric surface data are shown in FIG.39. TTL is 5.5135 mm. Fno is 1.6862. The image height is 3.528 mm. HFOVis 36.7581 degrees.

Ninth Example

Please refer to FIG. 22 which illustrates the ninth example of theoptical imaging lens set 1 of the present invention. Please refer toFIG. 23A for the longitudinal spherical aberration on the image plane 71of the ninth example; please refer to FIG. 23B for the astigmaticaberration on the sagittal direction; please refer to FIG. 23C for theastigmatic aberration on the tangential direction, and please refer toFIG. 23D for the distortion aberration. The components in the ninthexample are similar to those in the first example, but the optical datasuch as the curvature radius, the refractive power, the lens thickness,the lens focal length, the aspheric surface or the back focal length inthis example are different from the optical data in the first example,and in this example, the object-side surface 31 facing toward the objectside 2 has a convex part 33′ in the vicinity of the optical axis and theobject-side surface 61 facing toward the object side 2 has a concavepart 63′ in the vicinity of the optical axis.

The optical data of the ninth example of the optical imaging lens setare shown in FIG. 40 while the aspheric surface data are shown in FIG.41. TTL is 5.6143 mm. Fno is 1.7124. The image height is 3.528 mm. HFOVis 39.3455 degrees. In particular, 1) the HFOV of the ninth example islarger than that of the first example of the present invention.

Some important ratios in each example are shown in FIG. 42. The distancebetween the image-side surface 62 of the sixth lens element 60 to thefilter 70 along the optical axis 4 is G6F; the thickness of the filter70 along the optical axis 4 is TF; the distance between the filter 70 tothe image plane 71 along the optical axis 4 is GFP; the distance betweenthe image-side surface 62 of the sixth lens element 60 and the imageplane 71 along the optical axis 4 is BFL. Therefore, BFL=G6F+TF+GFP.

In the light of the above examples, the inventors observe at least thefollowing features of the lens arrangement of the present invention andthe corresponding efficacy:

1. The third lens element and the fourth lens element may be attached toeach other by glue or a film to render no air gap disposed between theimage-side surface 32 of the third lens element 30 and the object-sidesurface 41 of the fourth lens element 40.

2. The positive refractive power of the first lens element facilitatesthe concentration of light.

3. The image-side surface with a concave portion of the second lenselement in a vicinity of the optical-axis facilitates the correction ofthe spherical aberration of the first lens element.

4. No air gap disposed between the third lens element and the fourthlens element facilitates to greatly lower the problem of flare which iscaused by the total reflection of imaging light which passes through thefirst three lens elements.

5. The conditional formulae 16≤υ3−υ4≤50 make the third lens element andthe fourth lens element have a smoother shape to solve the problems ofinjection molding such as smaller thickness of the third lens elementand the fourth lens element or heavily crooked periphery curves of thethird lens element and the fourth lens element in order to correct thespherical aberration and the chromatic aberration which are caused bythe first two lens elements.6. The fourth lens element has an image-side surface with a convex partin the vicinity of the optical axis. It facilitates the correction ofthe aberration caused by the previous three lens elements.7. At least one of the object-side surface and the image-side surface ofthe fifth lens element is aspherical. It facilitates the adjustment ofthe aberration caused by the previous four lens elements.8. Both the object-side surface and the image-side surface of the sixthlens element are aspherical. They make the correction of the aberrationof high order easier.

In addition, the inventors further discover that there are some betterratio ranges for different data according to the above various importantratios. Better ratio ranges help the designers to design a betteroptical performance and an effectively reduce length of a practicallypossible optical imaging lens set. For example:

1. When the optical lens set satisfies the conditional formulaALT/AAG≤4.5 or TL/AAG≤5.5, it facilitates the correction of longitudinalspherical aberration to go with the third lens element and the fourthlens element. It is preferably 2.5≤TL/AAG≤5.5 or 1.5≤ALT/AAG≤4.5.2. EFL/(T₁+T₆)≤4.15 or EFL/(T₃+T₅)≤5.15 restricts the relationshipsbetween the focal length and the lens thickness. It goes withALT/EPD≤1.75 or TL/EPD≤4.5 to restrict the relationships between thelens thickness and the entrance pupil diameter to lower the Fno withoutcompromising the imaging quality. It is preferably 1.3≤EFL/(T₁+T₆)≤4.15,2.0≤EFL/(T₃+T₅)≤5.15, 0.8≤ALT/EPD≤1.75, 1.2≤TL/EPD≤4.5.3. With respect to T₁/G₂₃≤2.4, (T₁+G₁₂)/G₄₅≤2.15, (T₁+G₁₂+T₂)/T₃≤2.75,(T₂+T₄)/(G₁₂+G₃₄+G₅₆)≤3.8, AAG/T₁≤3.45, AAG/T₄≤4.8, ALT/AAG≤4.5,T₁/G₄₅≤1.95, (T₁+G₁₂)/G₂₃≤2.65, (T₁+G₁₂+T₂)/T₅≤1.85, T₅/(G₁₂+G₃₄+G₅₆)≤4,(T₂+G₂₃)/(G₁₂+G₃₄+G₅₆)≤3.3, AAG/T₂≤5.7, AAG/T₆≤3.6, it is preferably1.2≤T₁/G₂₃≤2.4, 0.7≤(T₁+G₁₂)/G₄₅≤2.15, 1.15≤(T₁+G₁₂+T₂)/T₃≤2.75,0.5≤(T₂+T₄)/(G₁₂+G₃₄+G₅₆)≤3.8, 0.7≤AAG/T₁≤3.45, 1.4≤AAG/T₄≤4.8,1.5≤ALT/AAG≤4.5, 0.65≤T₁/G₄₅≤1.95, 1.4≤(T₁+G₁₂)/G₂₃≤2.65,0.8≤(T₁+G₁₂+T₂)/T₅≤1.85, 0.5≤T₅/(G₁₂+G₃₄+G₅₆)≤4,0.5≤(T₂+G₂₃)/(G₁₂+G₃₄+G₅₆)≤3.3, 2.2≤AAG/T₂≤5.7 or 1.5≤AAG/T₆≤3.6 inorder to keep each thickness of the lens element and each air gap inpreferred ranges. A good ratio helps to control the lens thickness orthe air gaps to maintain a suitable range and keeps a lens element frombeing too thick to facilitate the reduction of the overall size or toothin to assemble the optical imaging lens set.

In the light of the unpredictability of the optical imaging lens set,the present invention suggests the above principles to have a shortertotal length of the optical imaging lens set, a larger apertureavailable, a wider field angle, better imaging quality or a betterfabrication yield to overcome the drawbacks of prior art. The abovelimitations may be properly combined at the discretion of persons whopractice the present invention and they are not limited as shown above.

The above-mentioned one or more conditions may be optionally combined inthe embodiments of the present invention. In addition to the aboveratios, the curvatures of each lens element or multiple lens elementsmay be fine-tuned to result in more fine structures to enhance theperformance or the resolution. For example, the object-side surface ofthe first lens element may additionally have a convex part in thevicinity of the optical axis. The above limitations may be properlycombined in the embodiments without causing inconsistency.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An optical imaging lens set, from an object sidetoward an image side in order along an optical axis comprising: a firstlens element, a second lens element, a third lens element, a fourth lenselement, a fifth lens element and a sixth lens element, said first lenselement to said sixth lens element each having an object-side surfacefacing toward the object side as well as an image-side surface facingtoward the image side, wherein: said first lens element has positiverefractive power and an image-side surface with a concave portion in avicinity of said optical-axis; said second lens element has animage-side surface with a concave portion in a vicinity of saidoptical-axis; no air gap between said third lens element and said fourthlens element; at least one of said object-side surface and saidimage-side surface of said fifth lens element is aspherical; and bothsaid object-side surface and said image-side surface of said sixth lenselement are aspherical; the optical imaging lens set exclusively has sixlens elements with refractive power, said sixth lens elements has asixth lens element thickness T₆ along said optical axis, TL is adistance between said object-side surface of said first lens element andsaid image-side surface of said sixth lens element along said opticalaxis and AAG is a sum of all five air gaps between each lens elementsfrom said first lens element to said sixth lens element along saidoptical axis to satisfy TL/AAG≤5.5 and AAG/T₆≤3.6.
 2. The opticalimaging lens set of claim 1, wherein υ3 is an Abbe number of said thirdlens element and υ4 is an Abbe number of said fourth lens element tosatisfy 16≤υ3−υ4≤50.
 3. The optical imaging lens set of claim 1, whereinsaid first lens element has a first lens element thickness T₁ along saidoptical axis and an air gap G₂₃ between said second lens element andsaid third lens element along said optical axis to satisfy T₁/G₂₃≤2.4.4. The optical imaging lens set of claim 1, wherein said first lenselement has a first lens element thickness T₁ along said optical axis,an air gap G₁₂ between said first lens element and said second lenselement along said optical axis and an air gap G₄₅ between said fourthlens element and said fifth lens element along said optical axis tosatisfy (T₁+G₁₂)/G₄₅≤2.15.
 5. The optical imaging lens set of claim 1,wherein said first lens element has a first lens element thickness T₁along said optical axis, said second lens element has a second lenselement thickness T₂ along said optical axis, said third lens elementhas a third lens element thickness T₃ along said optical axis and an airgap G₁₂ between said first lens element and said second lens elementalong said optical axis to satisfy (T₁+G₁₂+T₂)/T₃≤2.75.
 6. The opticalimaging lens set of claim 1, wherein said second lens element has asecond lens element thickness T₂ along said optical axis, said fourthlens element has a fourth lens element thickness T₄ along said opticalaxis, an air gap G₁₂ between said first lens element and said secondlens element along said optical axis, an air gap G₃₄ between said thirdlens element and said fourth lens element along said optical axis and anair gap G₅₆ between said fifth lens element and said sixth lens elementalong said optical axis to satisfy (T₂+T₄)/(G₁₂+G₃₄+G₅₆)≤3.8.
 7. Theoptical imaging lens set of claim 1, wherein said first lens element hasa first lens element thickness T₁ along said optical axis to satisfyAAG/T₁≤3.45.
 8. The optical imaging lens set of claim 1, wherein saidfourth lens element has a fourth lens element thickness T₄ along saidoptical axis to satisfy AAG/T₄≤4.8.
 9. The optical imaging lens set ofclaim 1, wherein EFL is an effective focal length of the optical imaginglens set, said first lens element has a first lens element thickness T₁along said optical axis to satisfy EFL/(T₁+T₆)≤4.15.
 10. The opticalimaging lens set of claim 1, wherein ALT is a total thickness of all sixlens elements along said optical axis and EPD is an entrance pupildiameter of an aperture stop to satisfy ALT/EPD≤1.75.
 11. The opticalimaging lens set of claim 1, wherein TL is a distance between saidobject-side surface of said first lens element and said image-sidesurface of said sixth lens element along said optical axis and EPD is anentrance pupil diameter of an aperture stop to satisfy TL/EPD≤4.5. 12.An optical imaging lens set, from an object side toward an image side inorder along an optical axis comprising: a first lens element, a secondlens element, a third lens element, a fourth lens element, a fifth lenselement and a sixth lens element, said first lens element to said sixthlens element each having an object-side surface facing toward the objectside as well as an image-side surface facing toward the image side,wherein: said first lens element has positive refractive power and animage-side surface with a concave portion in a vicinity of saidoptical-axis; said second lens element has an image-side surface with aconcave portion in a vicinity of said optical-axis; no air gap betweensaid third lens element and said fourth lens element; at least one ofsaid object-side surface and said image-side surface of said fifth lenselement is aspherical; and both said object-side surface and saidimage-side surface of said sixth lens element are aspherical; theoptical imaging lens set exclusively has six lens elements withrefractive power, said sixth lens element has a sixth lens elementthickness T₆ along said optical axis, ALT is a total thickness of allsix lens elements along said optical axis and AAG is a sum of all fiveair gaps between each lens elements from said first lens element to saidsixth lens element along said optical axis to satisfy ALT/AAG≤4.5 andAAG/T₆≤3.6.
 13. The optical imaging lens set of claim 12, wherein saidfirst lens element has a first lens element thickness T₁ along saidoptical axis and an air gap G₄₅ between said fourth lens element andsaid fifth lens element along said optical axis to satisfy T₁/G₄₅≤1.95.14. The optical imaging lens set of claim 12, wherein said first lenselement has a first lens element thickness T₁ along said optical axis,an air gap G₁₂ between said first lens element and said second lenselement along said optical axis and an air gap G₂₃ between said secondlens element and said third lens element along said optical axis tosatisfy (T₁+G₁₂)/G₂₃≤2.65.
 15. The optical imaging lens set of claim 12,wherein said first lens element has a first lens element thickness T₁along said optical axis, said second lens element has a second lenselement thickness T₂ along said optical axis, said fifth lens elementhas a fifth lens element thickness T₅ along said optical axis and an airgap G₁₂ between said first lens element and said second lens elementalong said optical axis to satisfy (T₁+G₁₂+T₂)/T₅≤1.85.
 16. The opticalimaging lens set of claim 12, wherein said fifth lens element has afifth lens element thickness T₅ along said optical axis, an air gap G₁₂between said first lens element and said second lens element along saidoptical axis, an air gap G₃₄ between said third lens element and saidfourth lens element along said optical axis and an air gap G₅₆ betweensaid fifth lens element and said sixth lens element along said opticalaxis to satisfy T₅/(G₁₂+G₃₄+G₅₆)≤4.
 17. The optical imaging lens set ofclaim 12, wherein said second lens element has a second lens elementthickness T₂ along said optical axis, an air gap G₁₂ between said firstlens element and said second lens element along said optical axis, anair gap G₂₃ between said second lens element and said third lens elementalong said optical axis, an air gap G₃₄ between said third lens elementand said fourth lens element along said optical axis and an air gap G₅₆between said fifth lens element and said sixth lens element along saidoptical axis to satisfy (T₂+G₂₃)/(G₁₂+G₃₄+G₅₆)≤3.3.
 18. The opticalimaging lens set of claim 12, wherein said second lens element has asecond lens element thickness T₂ along said optical axis to satisfyAAG/T₂≤5.7.
 19. The optical imaging lens set of claim 12, wherein EFL isan effective focal length of the optical imaging lens set, said thirdlens element has a third lens element thickness T₃ along said opticalaxis and said fifth lens element has a fifth lens element thickness T₅along said optical axis to satisfy EFL/(T₃+T₅)≤5.15.